Three-stage hydrocarbon hydrocracking process



March 20, 1962 c. H. WATKINS THREE-STAGE HYDROCARBON HYDROCRACKINGPROCESS Filed April 25, 1960 QQQQ I @690 mm SE uev su IN VE/V TOR:

Char/es H. Watkins 4.. a QQQ A T TORNEXS United States Patent 3,026,260THREE-STAGE HYDROCARBON HYDRO- CRACKING PROCESS Charles H. Watkins,Arlington Heights, 111., assignor to Universal Oil Products Company, DesPlaines, 111., a corporation of Delaware Filed Apr. 25, 1960, Ser. No.24,594 17 Claims. (Cl. 208-68) The present invention relates to aprocess for the conversion of hydrocarbonaceous material into lowerboiling hydrocarbon products, and, in one embodiment, is directed towarda process for producing hydrocarbons boiling within the gasoline andmiddle-distillate boiling ranges and substantially free from nitrogenouscompounds, from hydrocarbons boiling at a temperature in excess of themiddle-distillate boiling range, the latter being contaminated bysubstantial quantities of nitrogenous compounds.

Hydrocracking, or destructive hydrogenation, as distinguished from therelatively simple addition of hydrogen to unsaturated bonds betweencarbon atoms, efiects definite changes in the molecular structure ofhydrocarbons. Hydrocracking may, therefore, be designated as crackingunder hydrogenation conditions in such a manner that the lower-boilinghydrocarbon products resulting therefrom are substantially moresaturated than when hydrogen, or material supplying the same, is notpresent. As presently practiced, hydrocracking processes are mostcommonly employed for the destructive conversion of various coals, tarsand heavy residual oils for the purpose of producing substantial yieldsof low boiling, saturated products; to some extent, there exists atleast partial conversion to intermediates which are suitable forutilization as domestic fuels. In many instances, heavier gas oilfractions, which find utilization as lubricating material, are alsoproduced. Although many of these hydrocracking processes, or destructivehydrogenation reactions, may be, and are, conducted on a strictlythermal basis, either in the absence, or presence, of hydrogen, thepreferred processing technique involves the utilization of a catalyticcomposite possessing a high degree of hydrocracking activity. To assureeffective catalytic action over an extended period of time, and from thestandpoint of producing an increased yield of liquid product havingimproved physical aud/or chemical characteristics, controlled orselective cracking is desirable in virtually all hydrocrackingprocesses. For example, the lower molecular weight products, consistingessentially of those hydrocarbons boiling within the normal gasolineboiling 0 range, usually have an increased octane rating, and, as such,are extremely suitable for subsequent utilization in catalytic reformingprocesses to further increase the octane rating. Similarly, controlledor selective hydrocracking results in an increased yield ofmiddle-distillate boiling range hydrocarbons which are substantiallyfree from high molecular weight unsaturated hydrocarbons.

Selective hydrocracking is of particular importance when processinghydrocarbons, and mixtures of hydrocarbons, having a boiling range inexcess of the gasoline and middle-distillate boiling ranges; that is,hydrocarbons and mixtures of hydrocarbons, a well as various hydrocarbonfractions, distillates and gas oils, having a boiling range indicatingan initial boiling point of at least about 650 F. or 700 F., and an endboiling point as high as 1000 F., or more. The controlled, or selectivehydrocracking of such hydrocarbon fractions results in greater yields ofhydrocarbons boiling within the gasoline and middle-distillate boilingrange; that is, those hydrocarbons and hydrocabon fractions having aboiling range indicating an end boiling point below about 650 F. toabout 700 F. Furthermore, the selective hydrocracking of such 3,926,260Patented Mar. 20, 1962 heavier hydrocarbon fractions results in asubstantially increased yield of gasoline boiling range hydrocarbons;that is, those hydrocarbons and hydrocarbon fractions boiling within therange of from about F. to about 400 F. or 450 F., containing iso andnormal butanes, as the particular case warrants. The necessity forhydrocracking selectivity exists in order to avoid the decomposition ofnormally liquid hydrocarbons substantially or completely into normallygaseous hydrocarbons, the latter being inclusive of methane, ethane andpropane. The ultimate volumetric yield of normally liquid hydrocarbons,especially those boiling within the gasoline boiling range, as aninherent result of the excessive production of normally gaseoushydrocarbons, can be decreased to the extent Where the process is noteconomically feasible. Non-selective hydrocracking is distinguished fromcontrolled or selective hydrocracking in that the latter involves thesplitting of a higher-boiling hydrocarbon molecule into two hydrocarbonmolecules, both of which are normally liquid hydrocarbons. To a somewhatlesser degree selective hydrocracking involves the controlled removal ofmethyl, ethyl and propyl groups, which, in the presence of hydrogen, areconverted to methane, ethane and propane, the latter being referred toas light parafiinic hydrocarbons. In selective hydrocracking, theremoval of the aforesaid radicals is controlled such that not more thanone, or possibly two of such radicals are removed from a given molecule.For example, in the presence of hydrogen, and under selectivehydrocracking conditions, normal decane may be reduced to two pentanemolecules, normal heptane reduced to hexane, and nonane reduced tooctane or heptane, etc. Conversely, uncontrolled or non-selectivehydrocracking, will result in the decomposition of normally liquidhydrocarbons into the aforesaid normally gaseous hydrocarbons; forexample, through the continuous demethylation of normal heptane toproduce seven methyl groups which, in the presence of hydrogen, areconverted to seven molecules of methane. Thus, hydrocracking reactionswhich are permitted to run rampant can be seen to effect seriously theeconomic considerations of a given process.

Another disadvantage of non-selective or uncontrolled hydrocracking isthat such hydrocracking results in a more rapid formation of increasedquantities of coke and other heavy carbonaceous material which becomesdeposited upon the catalytic composite employed, and decreases, or evendestroys, the activity thereof to catalyze the desired reactions in thedesired manner. Such deactivation inherently results in a shorterprocessing cycle or period, with the attendant necessity of morefrequent regeneration of the catalyst, or total replacement thereof withfresh catalyst. Gf further significance, in regard to the hydrocrackingreaction, especially the economic considerations thereof, are theaspects of hydrogen production and consumption, the preservation ofaromatic compounds which boil within the gasoline boiling range, and theproduction of a liquid product substantially free from low molecularweight, unsaturated hydrocarbons. The deactivation of the catalyst,through the deposition of coke and other heavy carbonaceous material, orother means, appears to inhibit the hydrogenation activity to the extentthat a significant proportion of the gasoline boiling range hydrocarbonsconsists of unsaturated parafa'ins whereby the same is not highlysuitable for subsequent direct processing by catalytic reforming. On theother hand, selective hydrocracking does not tend to effect substantialhydrogenation, or saturation, of the aromatic compounds boiling withinthe gasoline boiling range, or the destructive hydrogenation of lowmolecular weight, straight or branched-chain hydrocarbons into normallygaseous hydrocarbons. Aromatic hydrocarbons, boiling within the gasolineboiling range, possess a relatively high octane blending value, and are,therefore, utilized to great advantage in increasing the anti-knockcharacteristics of a given gasoline boiling range traction. In addition,selective hydrocracking, although inhibiting the saturation of aromaticcompounds, does not necessarily result in the production of an excessivequantity of the lower molecular weight, unsaturated paratfinichydrocarbons.

Investigations have indicated that the relatively rapid deactivation ofa hydrocracking catalytic composite results from the presence ofnitrogen-containing compounds within the hydrocracking charge stock.These nitrogenous compounds, such as naturally-occurring, organicnitrogenous compounds, examples of which include pyrroles, amines,indoles, and other classifications of organic compounds, result in thedeactivation of the catalytically active metallic components, as well asthe refractory inorganic oxide carrier material which acts as the acidiccomponent of a great variety of hydrocracking catalysts. Suchdeactivation appears to result through the reaction of the nitrogenouscompounds with the various catalytic components, the extent of suchdeactivation steadily increasing as the process continues, and as thenitrogencontaining feed stock continues to contaminate the catalystthrough contact therewith. It is believed that neutraiization, occurringwhen the basicity of the nitrogenous compound reacts with the acidiccatalyst, resulting in a neutralization of the latter, is a factor to beconsidered in the deactivation of the catalyst, but is not thepredominating deactivating influence. The more predominating efiect,having the greatest influence in regard to catalyst deactivation, isbelieved to be the formation of a nitrogen-containing complex, throughinter-reaction with the catalytically active metallic components,whereby the active centers of the catalyst, normally available to thehydrocarbon charge stock, are effectively shielded therefrom.Deactivation of this nature is not believed to be a simple reversiblephenomenon which may be easily rectified by merely heating the catalystin the presence of hydrogen for the purpose of decomposing thenitrogen-containing complexes.

The primary object of the present invention is to provide ahydrocracking process which produces substantially greater yields ofhydrocarbons boiling within the gasoline and middle-distillate boilingranges, without the attendant saturation of aromatic compounds and theuncontrolled cracking of the low molecular weight hydrocarbons. Arelated object is to provide a process which permits the utilization ofpetroleum hydrocarbon charge stocks having an initial boiling point ashigh as about 700 to about 800 F. or more, which charge stocks containresidual nitrogenous compounds in excessive quantities of the order ofabout 1000 ppm. to about 5000 p.p.rn., such concentrations otherwiseresulting in the rapid deactivation of the catalytic composite employed.

In one embodiment, the present invention relates to a process forconverting hydrocarbonaceous material, having a boiling range in excessof the gasoline boiling range, into lower boiling hydrocarbon productswhich comprises cracking said hydrocarbonaceous material in a firstreaction zone, separating the resultant efliuent into a light fractionand a heavy fraction containing hydrocarbons having an initial boilingpoint in excess of a temperature of about 800 F.; reacting said lightfraction with hydrogen in a second reaction zone, passing at least aportion of the effluent therefrom, along with additional hydrogen, intoa third reaction zone maintained at hydrocracking conditions; separatingthe resultant normally liquid hydrocarbons into a first fraction havingan end boiling point of about 400 F. to about 450 F., a second fractionhaving an end boiling point of about 650 F. to about 700 F., and a thirdfraction boiling at a temperature in excess of about 650 F. to about 700F., and recycling at least a portion of said third fraction to combinewith the efiiuent from said second reaction zone and hydrogen, prior toconversion thereof in said third reaction zone.

The present invention is directed toward a three-stage process forconverting hydrocarbonaceous material having a boiling range of fromabout 700 F. to about 1000 F., and containing nitrogenous compounds,into lower boiling hydrocarbon products, which process comprisesinitially fractionating said hydrocarbonaceous material to produce afirst light fraction containing those hydrocarbons boiling below about800 F. and a first heavy fraction having an initial boiling point ofabout 800 F., cracking said first heavy fraction in a first reactionzone containing a catalyst comprising at least one metallic componentselected from the metals of groups VIA and the iron-group of theperiodic table, and mixtures thereof, separating the resultant efi'luentinto a second light fraction and a second heavy fraction, the latterhaving an initial boiling point of about 800 F., recycling said secondheavy fraction to combine with said first heavy fraction prior toconversion in said first reaction zone, and combining said second lightfraction with said first light fraction; reacting the resultant lightfraction mixture in a second reaction zone and in contact with acatalyst comprising from about 4% to about 45% by weight of molybdenum,removing ammonia and normally gaseou hydrocarbons from the resultantsecond zone eflluent, and passing the normally liquid hydrocarbons,along with additional hydrogen, into a third reaction zone maintained athydrocracking conditions; removing normally gaseous hydrocarbons fromthe third reaction zone efiluent and separating the normally liquidhydrocarbons into a first fraction having an end boiling point of about400 F. to about 450 F., a second fraction having an initial boilingpoint of about 400 F. to about 450 F. and an end boiling point of about650 F. to about 700 F., and a third fraction boiling at a temperature inexcess of about 650 F. to about 700 F., recycling at least a portion ofsaid third fraction to combine with said hydrogen and the normallyliquid hydrocarbons from said second reaction zone, prior to conversionthereof in said third reaction zone.

A more specific embodiment of the present invention involves a processfor converting nitrogen-contaminated hydrocarbonaceous material, havinga boiling range of from about 700 F. to about 1000 E, into lower boilinghydrocarbon products substantially free from nitrogenous compounds,which process comprises initially stabilizing said hydrocarbonaceousmaterial to produce a first light fraction containing those hydrocarbonsboiling below about 800 F., and a first heavy fraction having an initialboiling point of about 800 F.; cracking said first heavy fraction in afirst reaction zone containing a cracking catalyst comprising at leastone metallic component from the metals of groups VIA and the irongroupof the periodic table, and mixtures thereof, separating the resultantefiiuent into a second light fraction and a second heavy fractioncontaining hydrocarbons boiling in excess of a temperature of about 800F., recycling the second heavy fraction to combine with said first heavyfraction prior to the conversion thereof in said first reaction zone,and combining said second light fraction with said first light fraction;reacting the resulting light fraction mixture with hydrogen in a secondreaction zone containing a catalyst comprising from about 4% to about 45by weight of molybdenum, removing ammonia and normally gaseoushydrocarbons from the resultant second zone efiluent, and passing thenormally liquid hydrocarbons, along with additional hydrogen, into athird reaction zone maintained at hydrocracking conditions andcontaining a catalyst comprising from about 0.01% to about 5.0% byweight of palladium composited with silica and from about 10% to aboutby weight of alumina; removing normally gaseous hydrocarbons from theresultant third zone eifiuent and separating the normally liquidhydrocarbons into a first fraction having an end boiling point of about400 F. to about 450 F., a second fraction having an initial boilingpoint of about 400 F. to about 450 F., and an end boiling point of about650 F., to about 700 F., and a third fraction boiling at a temperaturein excess of about 650 F. to about 700 F., recycling at least a portionof said third fraction to combine with the normally liquid hydrocarbonsfrom said second reaction Zone and hydrogen, prior to conversion thereofin said third reaction zone.

The three-stage process of the present invention may be more clearlyillustrated and understood by initially defining several of the termsand phrases as employed Within the present specification and theappended claims. The term, hydrocarbons, or hydrocarbonaceou material,is intended to connote saturated hydrocarbons, straightchain andbranched-chain hydrocarbons, unsaturated hydrocarbons, aromatic andnaphthenic hydrocarbons, as well as mixtures of various hydrocarbonssuch as hydrocarbon fractions and/ or hydrocarbon distillates, etc. Thephrase, hydrocarbons boiling Within the gasoline boiling range, orgasoline boiling range hydrocarbons, is intended to connote thosehydrocarbons boiling at a temperature of from about 100 F. to about 400F. or 450 F.; that is, hydrocarbon fractions having an initial boilingpoints (as determined by Standard ASTM distillation methods) of about100 F., and an end boiling point within the range of about 400 F. toabout 450 F. Gasoline boiling range hydrocarbons i intended to includehydrocarbon mixtures having the aforesaid boiling range, and inclusiveof iso and normal butanes. The term, light parafiinic hydrocarbons, isintended to con- .note those hydrocarbons containing three or lesscarbon atoms; that is, methane, ethane and propane. Therefore,hydrocarbons boiling at a temperature in excess of the gasoline boilingrange is intended to connote those hydrocarbons and mixtures ofhydrocarbons which possess an initial boiling point in excess of about400 F. to about 450 F. The term, middle-distillate, or light gas oil,refers to those hydrocarbon fractions having an initial boiling pointwithin the range of about 400 F. to about 450 F. and an end boilingpoint within the range of about 650 F. to about 700 F. Similarly, inregard to the various catalytic composites employed within the threeindividual reaction zones of the present process, and in one embodimentin two of the three reaction zones, the term, metallic component, orcatalytically active metallic component," is intended to encompass thosecomponents which are employed for their hydrocracking activity, or fortheir propensity for the destructive removal of nitrogenous compounds,as the case may be. In this manner, the catalytically active metalliccomponents are distinguished from those components which are employed asthe solid support, or carrier material, or the acidic crackingcomponent. As hereinafter set forth in greater detail, the process ofthe present invention consists of three integrated, but separate,stages. Each stage utilizes a distinct catalytic composite, difierent,in most applications of the present invention, from the catalyticcomposites employed in the other stages. The various catalyticcomposites will hereinafter be described in detail with reference to theparticular stage in which employed, and also in regard to the functionto be served.

The particular catalytically active metallic component, or components,regardless of the stage in which employed, are composited with asuitable, solid carrier material, which may be eithernaturally-occurring, or syntheticallyprepared. Naturally-occurringcarrier materials, include various aluminum silicates, particularly whenacid-treated to increase the activity thereof, variousalumina-containing clays, earths, sand, and the like;synthetically-prepared carrier material generally includes at least aportion of both silica and alumina. Other suitable carrier materialcomponents which may, in particular instances, be combined in anintegral portion of the synthetically-prepared carrier material, arezirconia, magnesia, thoria, boria, titania, etc. The preferredhydrocracking catalyst component, for use in the third stage, comprisesa composite of silica and from about 10% to about 90% by weight ofalumina, and still more preferably, a composite of silica and from about25% to about by weight of alumina. As hereinabove stated, the process ofthe present invention involves the utilization of three separate,distinct reaction zones, each of which contains a catalyst Whosecomposition depends, at least in part, upon the function to be servedwithin such reaction zone, and, therefore, these catalytic compositeswill hereinafter be described in greater detail.

As hereinbefore set forth, one embodiment of the present inventioninvolves a process for producing hydrocarbons which boil within thegasoline and middle-distillate boiling range, from those hydrocarbonswhich boil at a temperature in excess of the middle-distillate boilingrange. The three-stage process of the present invention encompasses atleast one hydrocracking reaction zone, which, in and of itself, has beenconsidered generally applicable to processing petroleum-derived feedstocks of the middle-distillate boiling range and above. Suitable chargestocks to hydrocracking processes are considered to include kerosinefractions, gas oil fractions, lubricating oil and white oil stocks,cycle stocks, fuel oil stocks, reduced crudes, the various high-boilingbottom recovered from the fractionating columns generally integratedwithin catalytic cracking operations, and referred to as heavy recyclestock, and other sources of hydrocarbons having a depreciated marketdemand due to the high boiling points of these hydrocarbons, accompaniedby the usual presence of asphaltic and other heavy hydrocarbonaceousresidues. The present invention is particularly directed towardprocessing the heavier of the aforementioned hydrocarbon feed stocks,namely, vacuum gas oil fractions, white oil stocks, heavy cycle stocks,fuel oil stocks, reduced crudes etc.; that is, those heavy hydrocarbonshaving an initial boiling point of at least about 650 F. to about 700 F.and an end boiling point of about 1000 F. or more. Generally, all ofthese sources of hydrocarbon feed stocks contain high-boilingnitrogenous compounds and sulfurous compounds as contaminants. Althoughthe major proportion of such nitrogenous compounds may be removed bymany known means, such as a hydrorefining pretreatment, it is verydifiicult, if not virtually impossible, to remove the last few parts permillion of nitrogen from the charge stock prior to subjecting the sameto the hydrocracking process. For example, a hydrorefining pretreatment,in which the feed stock is subjected to the action of a catalyst, atreaction conditions, will result in the conversion of the nitrogenous,organically-bound components into ammonia and the correspondinghydrocarbon residue. Although the structure of the hydrocarboncomponents are not substantially altered, the resulting hydrocarboncharge stock will, in all probability, contain a relatively minor amountof nitrogenous compounds, as compared to the excessive quantityoriginally present. Notwithstanding such quantities, these organicnitrogen compounds will eventually result in the deactivation ofhydrocracking catalyst, and particularly catalysts consisting of metalsfrom groups VI and VIII of the periodic table. For example, I have foundthat a catalyst comprising at least one platinum-group metalliccomponent, impregnated upon a silica-alumina carrier material, is a veryeffective catalyst for the hydrocracking of gas oils boiling below about800 F. However, these catalysts are virtually immediately poisoned byeither sulfurous or nitrogenous compounds, and particularly by thelatter. The contaminants, and particularly organically-bound nitrogenouscompounds, are very diflicult, if not impossible, to remove fromhydrocarbon fractions boiling above about 800 F., whereas virtuallycomplete removal may be effected from hydrocarbons boiling below about800 F.

Through the utilization of the threestage process of the presentinvention, particularly when processing hydrocarbon charge stocksboiling above about 700 F, to about 1000 F. or more, it is possible toproduce high volumetric yields of gasoline boiling range hydrocarbonswhile simultaneously maximizing the yield of middledistillatehydrocarbons which are substantially free from nitrogenous compounds. Asubstantial increase in the overall yield of gasoline boiling rangehydrocarbons may then be obtained by further processing nitrogen-free,middle-distillate material simultaneously produced by the presentprocess. The flexibility of the present process permits the withdrawalto storage of the middle-distillate hydrocarbon product for subsequentconversion to gasoline boiling range hydrocarbons when the marketabilityof the latter so requires.

The present three-stage process may be more clearly understood throughreference to the accompanying drawing which illustrates one embodimentthereof. It is not intended, however, to unduly limit the presentprocess to the particular embodiments indicated in the drawing. Variousflow valves, control valves, coolers, condensers, overhead refluxcondensers, pumps, compressors, heaters, knockout pots, etc., have beeneliminated, or greatly reduced, as not being essential to the completeunderstanding of the present process. The utilization of these, andother miscellaneous appurtenances will immediately be recognized by onepossessing skill in the art of petroleum processing; it is not intendedthat such modifications remove the process beyond the scope and spiritof the appended claims. Referring now to the drawing, the hydrocarbonchange stock, contaminated by a substantial quantity of nitrogenouscompounds, of the order of about 1000 p.p.m. to about 5000 p.p.m., andsulfurous compounds as high as about 3.0% to about 5.0% by weight,enters the process through line 1 into stabilizer 2. To illustrate aparticularly preferred embodiment of the present invention, the chargestock in line 1 is indicated as having an initial boiling point of about700 F. and an end boiling point of about 1000 F., as determined bystandard ASTM distillation. However, it is understood that the chargestock may be any of the heavy hydrocarbonaceous material previouslydescribed; for exampie, a reduced crude consisting entirely ofhydrocarbons boiling at a temperature in excess of 800 F. to 1000 F. ormore. The total liquid charge stock entering stabilizer '2 is separatedinto a first light fraction having an end boiling point of about 800 F.,shown as leaving stabilizer 2 via line 3, and a first heavy fractionhaving an initial boiling point of about 800 F., indicated as leavingsta- I bilizer 2 via line 4. This first heavy fraction is combined witha second heavy fraction, containing hydrocarbons boiling in excess ofabout 800 F., the mixture being passed through heater 6 and line 8 intocracking zone 9. The primary function, to be served by cracking zone 9,is the conversion of those hydrocarbons boiling in excess of atemperature of 800 F. into lower boiling hydrocarbon products which boilbelow about 800 F. Thus, cracking zone 9 may be a commonthermal-cracking reaction zone of the single-coil or double-coil type,in which instance the total liquid charge thereto is raised to thedesired thermal cracking temperature in heater 6, prior to enteringcracking zone 9 through line 8. In another embodiment, cracking zone 9may comprise a catalytic hydrocracking unit, in which event the totalliquid charge in line 4 is admixed with the requisite quantity ofhydrogen entering via line 5, the mixture being raised to the operatingtemperature in heater 6, passing through line 8 into cracking zone 9. Inthis latter instance, cracking zone 9 will contain a suitablehydrocracking catalyst which may be an iron-group metallic componentcomposited with a siliceous carrier material such as alumina and silica.Or, the hydrocracking catalyst may comprise an iron-group metalliccomponent promoted by a Group VIA metal such as molybdenum, chromiumand/ or tungsten. The first reaction zone, cracking zone 9, may be, inparticular processing schemes, a fluid catalytic cracking unit operatingin the absence of added hydrogen. It is understood that the preciseconversion means, illustrated in the drawing as cracking zone 9, bywhich those hydrocarbons boiling at a temperature in excess of about 800F, are converted to hydrocarbons boiling below about 800 F., is notconsidered to be a limiting feature of the present invention. 1 havefound that the nitrogenous compounds, contaminating the hydrocarboncharge stock entering line 1, are extremely diflicult to remove from theheavier hydrocarbons, that is, those hydrocarbons boiling in excess of800 F whereas these nitrogenous compounds are readily susceptible toremoval from those hydrocarbons boiling below about 800 F., especiallythrough the utilization of a particular catalytic composite ashereinafter set forth. In any event, the total effluent from crackingzone 9 passes through line 10 into separator 11 from which the normallyliquid hydrocarbons are removed via line 13 into fractionator 14.

Separator 11 serves to remove light parafiinic hydrocarbons, such asmethahe, ethane and propane, and other various gaseous components fromthe total effiuent entering through line 10, providing thereby anormally liquid hydrocarbon stream in line 13. The light parafiinic hydrocarbons are indicated as leaving separator 11 via line 12. Othergaseous components are removed from the normally liquid hydrocarbons inseparator 11, and include carbon monoxide, carbon dioxide, hydrogensulfide, ammonia, sulfur dioxide, and various oxides of nitrogen.Various modifications may be made to the separating means illustrated byseparator 11, whereby the overall flow pattern therein is changed, butthe function to be served, as well as the end result, remains the same.For example, the total gaseous phase, illustrated as leaving via line12, may be passed through a suitable absorbent material, whereby thelight paraffinic hydrocarbons are recovered substantially free fromhydrogen sulfide, ammonia, carbon dioxide, and the various oxides ofnitrogen and sulfur. Similarly, water may be injected into line 10, themixture entering a suitable liquid-liquid separating zone whereby theammonia is adsorbed in, and removed with the water phase, the lightparafiinic hydrocarbons and other gaseous components being removed asindicated by line 12, and the normally liquid hydrocarbons removed vialine 13. Various other modifications, in regard to the separating meansillustrated by separator 11, as well as those separating meanshereinafter described, and illustrated by separators 21 and 30, will beimmediately recognized by those possessing skill in the art of petroleumprocessing. It is not intended that these modifications, and those aboveset forth, remove the resulting flow from within the broad scope of thepresent invention. As illustrated, one of the essential features of thepresent invention is the initial preparation of a stream of normallyliquid hydrocarbons boiling below about 800 F and which pass throughline 13 into fractionator 14. Fractionator 14 is maintained undersuitable operating conditions, of temperature and pressure, such thatthe normally liquid hydrocarbons entering via line 13 are separated intoa second heavy fraction, containing those unreacted hydrocarbons boilingat a temperature in excess of 800 F. and a second light fractioncontaining those hydrocarbons having an end boiling point of about 800F. The second heavy fraction is removed from fractionator 14 via line 7and is combined With the first heavy fraction in line 4 leavingstabilizer 2. The second light fraction is removed from fractionator 14via line 15, and is admixed with the first light fraction leavingstabilizer 2 in line 3. The resulting light fraction mixture is admixedwith hydrogen, entering the system via line 16, and the total charge israised to the desired operating temperature, within the range of about500 F. to about 1000 F., in heater 17. The heated mixture of hydrogenand the light fractions from stabilizer 2 and fractionator 14 are passedvia line 18 into clean-up reaction zone 19. Clean-up zone 19 hasdisposed therein a catalytic composite comprising from about 4% to about45% by weight of molybdenum, calculated as the element. The reactionzone is maintained under operating conditions such that thesubstantially complete destruction of the nitrogenous compounds, as wellas the sulfurous compounds, contained within the charge stock, thelatter now consisting essentially of hydrocarbons boiling below about atemperature of 800 F., is effected. In addition, as hereinafter setforth, through the careful selection of both catalyst and operatingconditions, there will be efiected, in clean-up zone 19, a substantialdegree of hydrocarbon conversion whereby the heavier hydrocarbons, thoseboiling within the range of from about 650 F. to 800 F., are convertedinto hydrocarbons boiling below about 650 F., without experiencing theexcessive production of light .paraifinic hydrocarbons, methane, ethaneand propane. Furthermore, since the catalyst in clean-up zone 19 isselected for its nitrogeninsensitivity, the rapid deactivation of thecatalyst, otherwise resulting when hydrocracking suchnitrogen-containing charge stocks, is not experienced. The totaleflluent from reaction zone 19 is passed via line 20 into separator 21.As previously described With reference to separator 11, separator 21 isemployed to illustrate a separating means whereby the normally liquidhydrocarbons are recovered in line 23 substantially completely free fromlight parafiinic hydrocarbons and other gaseous material, indicated asleaving separator 21 through line 22. In addition, as a result of thecatalyst and operating conditions of clean-up zone 19, substantialquantities of hydrogen sulfide and ammonia are removed in separator 21.The normally liquid hydrocarbons in line 23 enter line 24, are admixedwith hydrogen entering the system via line 25, the entire mixturepassing into heater 26, and thereafter through line 27 intohydrocra'cking zone 28. The total charge to hydrocracking zone 28 willbe raised to a temperature, in heater 26, within the range of about 450F. to about 950 F; that is, the operating temperature of hydrocrackingzone 28 will be at least about 50 F. lower than the operatingtemperature of clean-up zone 19. The total effluent, including butanes,normally liquid hydrocarbons boiling within the range of from about 100F. to about 800 F., carbon monoxide, carbon dioxide, light parafiinichydrocarbons, etc., are passed through line 29 into separator 30. Thenormally liquid hydrocarbons, including butanes, are removed fromseparator 30" via line 32, and passed to side-cut fractionator 33 at apoint below centerwell 34. The light paraflinic hydrocarbons enteringseparator 30 are removed via line 31, and, as hereinbefore described,various other gaseous components are removed therefrom, such that onlynormally liquid hydrocarbons, but including butanes, are passed intoside-cut fractionator 33.

Fractionator 33 is maintained at suitable conditions of temperature andpressure whereby the butanes and normally liquid hydrocarbons having aninitial boiling point of about 100 F. and an end boiling point of about400 F., and containing less than about 0.1 'p.p.m. of nitrogen, areremoved via line 36. A second fraction, containing less than about 3.0ppm. of nitrogen, is removed from a point above centerwell 34, via line35. This second fraction contains those hydrocarbons boiling within themiddle-distillate boiling range, that is, having an initial boilingpoint of about 400 F. and an end boiling point of about 650 F. A thirdfraction, containing those unreacted hydrocarbons boiling within therange of from about 650 F. to about 800 F., are passed through line 24,combined, at least in part, Withth'e total normally liquid hydrocarboneffluent in line 23, further admixed with hydrogen in line 25, andrecycled to the system through heater 26 and line 27 into hydrocrackingzone 28.

From the foregoing description of the embodiment illustrated in theaccompanying drawing, it is readily ascertained that the process is, ineffect, a three-stage process for producing hydrocarbons boiling withinthe gasoline boiling range, and simultaneously for producing increasedyields of middleistillate boiling range hydrocarbons, the latter beingextremely suitable for direct processing to produce additional gasolineboiling range hydrocarbons. Various modifications may be made to theillustrated embodiment by those possessing skill within the art ofpetroleum processing, and it is not intended that such modificationsremove the process from the scope and spirit of the appended claims. Forexample, as hereinabove stated in regard to separators 11, 21 and 30,changes may be made whereby a somewhat difierent flow pattern andapparatus setup results. It is evident, however, that such a flowpattern will merely accomplish the same object resulting from the flowpattern illustrated within the drawing. An essential feature of theprocess of the present invention involves the threestage reaction zonesystem, whereby each stage individually performs a particular functionin a particular manner, the combinative effect being the production ofgasoline and middle-distillate boiling range hydrocarbons from thosehydrocarbons boiling in excess of a temperature of about 700 F., thelatter contaminated by substantial quantities of nitrogenous compoundsof the order of about 1000 ppm. to about 5000 ppm.

As hereinbefore set forth, the process of the present invention isparticularly directed to the processing of hydrocarbons and mixtures ofhydrocarbons boiling at temperatures in excess of the "gasoline boilingrange. However, it is most advantageously applied to petroleumderivedfeed stocks, particularly those stocks commonly considered as beingheavier than middle-distillate fractions. Such charge stocks include gasoil fractions, heavy vacuum gas oils, reduced cr'udes, lubricating oils,and white oil stocks, as well as high-boiling bottoms recovered fromvarious catalytic cracking operations. Therefore, although the chargestock to the present three stage process may have an initial boilingpoint of about 400 F. to about 450 F., and an end boiling point of about1000 F. or higher, the process affords additional benefits, and isparticularly directed toward the processing of hydrocarbon charge stockshaving significantly higher initial boiling points, that is, of theorder of at least about 650 F. to about 700 F. In further describing theprocess of the present invention, and the various limitations imposedthereupon, the process will be divided, in the interest of simplicity,into its three separate, distinctly individual stages.

Essentially, the first stage comprises a stabilizing column, heater andreaction zone, suitable liquid-gas separating means, and afractionator,'the latter employed for the purpose of separating thetotal normally liquid product efiluent into a light fraction having anend boiling point of about 800 F., and a heavy fraction having aninitial boiling point of about 800 F. The various components of thefirst stage are utilized in such a manner, and under such conditions asto result in the substantially complete conversion of the charge stockinto hydrocarbons boiling below 800 F. Although at least a portion ofthe charge stock is converted, in this first stage, to hydrocarbonsboiling Within the gasoline boiling range, the greater proportion of thecharge stock will be converted to hydrocarbons boiling within the rangeof from about 400 F. or 450 F. to about 800 F., the lighter fractionsserving as the charge stock to the second stage of the entire process.Briefly, therefore, the heavy hydrocarbon charge stock, for example, aheavy vacuum gas oil having a boiling range of from about 700 F. toabout 1000 F., or higher, and contaminated by nitrogenous compounds ofthe order of from about 1000 ppm.

'to about 5000 p.p.n1., and sulfurous compounds as high as about 3.0% toabout 5.0% by weight, is introduced into a stabilizing column for thepurpose of removing those hydrocarbons having an end boiling point ofabout 800 F. The remainder of the vacuum gas oil charge is admixed withhydrogen in an amount of from about 3000 to about 10,000 standard cubicfeet per barrel of such hydrocarbon charge, in those instances whereinthe first-stage of the process comprises a hydrocracking reaction zone.As hereinbefore set forth, the reaction zone comprising this first stagemay be a thermal-cracking unit of the single-coil or double-coil type.It is preferred, however, in order to avoid the unnecessary, excessiveproduction of light parafiinic hydrocarbons, normally resulting from athermal cracking unit, or fluid catalytic cracking unit, to employcatalytic hydrocracking within the first stage of the process. In thelatter instance, the mixture of hydrogen and those hydrocarbons boilingabove about 800 F., is heated to the desired operating temperature, offrom about 500 F. to about 1500 F., and thereafter passed into the firstreaction zone. The reaction zone will be maintained under an imposedpressure within the range of from about pounds to about 3000 pounds persquare inch, and at a temperature within the aforesaid range; theprecise operating conditions will be dependent upon the various physicaland/ or chemical characteristics of the particular heavy hydrocarboncharge being processed, and upon the type of cracking unit employed.Higher pressures appear to favor the destructive conversion of thosehydrocarbons boiling in excess of about 800 F., and are, therefore,preferred; thus, the first reaction zone will preferably operate underan imposed pressure within the range of about 100 to about 3000 poundsper square inch. When utilized as a hydrocracking zone, as distinguishedfrom a simple thermalcracking zone, the first reaction zone will containa hydrocracking catalyst comprising at least one metallic component fromthe metals of groups VIA and the iron-group of the periodic table, andmixtures thereof. Thus, the catalyst will comprise one or more of thefollowing: chromium, molybdenum, tungsten, iron, cobalt, and nickel.Regardless of the component, or components, they are composited with asuitable carrier material, and preferably one which contains substantialquantities of silica. Thus, the hydrocracking catalyst employed in thefirst reaction zone may comprise from about to about 50% by weight ofnickel, and a composite of alumina and from about 65% to about 95% byweight of silica. Lesser quantities of the group VIA metallic componentswill be employed, and will lie within the range of from about 2.0% toabout 20.0% by weight thereof. In any event, the hydrocarbon chargestock will contact the particular catalyst employed at a liquid hourlyspace velocity within the range of from about 0.3 to about 10.0; arelatively lower range of liquid hourly space velocity is preferred,that is, from about 0.3 to about 3.0. Although the first reaction zoneis designed to serve a single function, that of converting thosehydrocarbons boiling above about 800 F. into hydrocarbons boiling belowabout 800 F., there will be effected at least partial removal of thesulfurous and nitrogenous compounds. The resulting ammonia and hydrogensulfide, in addition to light parafiinic hydrocarbons, carbon monoxideand carbon dioxide, and the normally liquid hydrocarbons includingbutanes, are passed into a suitable separating means whereby thebu-tanes and normally liquid hydrocarbons are recovered substantiallyfree from the light parafiinic hydrocarbons and the aforementionedgaseous products. The normally liquid hydrocarbons are then subjected tofractionation to provide a light fraction comprising the materialboiling below about 800 F., which light fraction is combined with theinitial light fraction from the initial stabilizing procedure, therebyforming the charge to the second stage of the process. Thosehydrocarbons which boil above a temperature of about 800 F. are recycledto combine with the heavy fraction from the 12 initial stabilizing step,thereby forming the total liquid charge to this first reaction zone.

Similarly, the second-stage of the present process comprises at least aheater, reaction zone, and separating means similar to that described inregard to the first stage of the process. The total liquid charge to thesecond stage of the process, now consisting essentially of hydrocarbonsboiling below a temperature of about 800 F., is admixed with hydrogen inan amount of from about 1000 to about 8000 Standard cubic feet perbarrel. The mixture of hydrogen and liquid hydrocarbons is raised to atemperature of from about 500 F. to about 1000 R, and passed into thesecond reaction zone, maintained under an imposed pressure of about 300to about 3000 pounds per square inch, the catalyst in which secondreaction zone serves a particular dual function. The liquid charge rateis equivalent to a liquid hourly space velocity of about 0.1 to about10.0. Thas is, the catalyst is nonsensitive to the presence ofsubstantial quantities of both nitrogenous compounds and sulfurouscompounds, while effecting the destructive removal thereof, and alsoeffects a significant degree of conversion of those hydrocarbons boilingat a temperature in excess of about 650 F. into those hydrocarbonsboiling within the gasoline and middle-distillate boiling ranges. I havefound that a catalyst comprising relatively large quantities ofmolybdenum, calculated as the element, and composited with a suitablecarrier material such as alumina, is particularly eflicient in carryingout the desired dual operation of the second reaction zone. Aparticularly preferred catalytic composite, for utilization in thisfirst reaction zone, comprises from about 4.0% to about 45.0% by weightof molybdenum, and utilizes alumina as the sole refractory inorganicoxide within the carrier material. It is preferred to utilize alumina inthe absence of other refractory inorganic oxides, such as silica,zirconia, magnesia, titania, thoria, boria, etc. Although theserefractory inorganic oxides may be employed in relatively minorquantities, with respect to the amount of alumina, they appear to impartadditional cracking activity to the catalyst Within the second reactionzone, such that those hydrocarbons boiling in excess of about 650 F. aresubjected to non-selective cracking whereby excessive quantities oflight paraffinic hydrocarbons are produced therefrom. In addition to theaforementioned major proportion of molybdenum, minor quantities ofnickel, iron and/or cobalt, from about 0.2% to about 6.0% may beemployed. The precise composition of the catalytic composite employed inthe second reaction zone will, of course, depend to a great extent uponthe physical and chemical characteristics of the liquid chargetherethrough.

The gaseous ammonia and hydrogen sulfide, resulting from the destructiveremoval of nitrogenous and sulfurous compound-s within the secondreaction zone, are removed from the total efliuent in any suitablemanner. For example, the total effluent may be admixed with Water, andthereafter subjected to separation such that the ammonia is adsorbedwithin the water-phase. Or, the total reaction zone efiluent may bepassed into a separation zone, countercurrently to a liquid adsorbent,whereby the ammonia, hydrogen sulfide, and other gaseous components areefiectively completely removed therefrom. In addition to the removal ofhydrogen sulfide and ammonia, it is desired that the few lightparafiinic hydrocarbons, methane, ethane, and propane, resulting fromthe hydrocarbon conversion within the second reaction zone, are alsoremoved from the total eflluent therefrom. Therefore, the separatingzone may comprise a low-temperature flash chamber whereby the ammonia,hydrogen sulfide and light parafinic hydrocarbons are removed as a gasphase. In any event, the normally liquid hydrocarbons, which may or maynot include butanes, substantially completely free from nitrogenouscompounds, are utilized as the liquid charge to the third stage of thepresent process.

The third stage of the present process is designed to convert the nownitrogen and sulfur free hydrocarbons boiling within the range of fromabout 650 F. to about 800 F., into hydrocarbons boiling within thegasoline and middle-distillate boiling ranges. The charge to the thirdstage, being the total normally liquid hydrocarbons, including butanes,discharging from the second-stage separating means, is admixed withhydrogen in an amount of from about 1000 to about 6000 standard cubicfeet per barrel of total liquid charge. The quantity of hydrogen,employed within the third reaction zone, may be less than that requiredin either of the two preceding zones. This is due to the physical andchemical characteristics of the charge stock, whereby such charge stockreadily lends itself to comparatively mild hydrocracking conditionswithin the third stage of the process. Therefore, although the thirdstage may operate acceptably at an imposed pressure within the range offrom about 1000 to about 3000 pounds per square inch, excellent resultsmay be achieved through the utilization of lower pressures, within therange of from about 500 to about 1500 pounds per square inch. Similarly,the temperature at which the third reaction zone is maintained, may besignificantly less than the temperature in either of the two precedingzones. For example, as hereinbefore stated, the second reaction zone ismaintained at a temperature within the range of about 500 to about 1000F. The third reaction zone operates at a temperature at least about 50F. lower than the aforesaid range; it is not uncommon, in the process ofthe present invention, to permit the third reaction zone to operate at atemperature level as much as 100 F. to 200 F. lower than that in thesecond reaction zone. Thus, the third reaction zone may be maintainedunder the relatively mild hydrocracking conditions of from about 400 F.to about 800 F. Similarly, the liquid hourly space velocity through thethird reaction zone may be significantly higher, within the range offrom about 1.0 to about 10.0.

The catalyst employed within the third reaction zone compri es at leastone metallic component selected from the metals of groups VIA and VHI ofthe periodic table. The metallic component of the catalyst utilizedwithin the third stage of the present process may comprise mixtures oftwo or more of such metals. Thus, the catalyst employed in the thirdreaction zone may consist of chromium, molybdenum, tungsten, iron,cobalt, nickel, palladium, platinum, ruthenium, rhodium, osmium,iridium, and mixtures of two or more including nickel-molybdenum,nickel-chromium, molybdenum-platinum, cobaltnickel-molybdenum,molybdenum-palladium, chromiumplatinum, chromium-palladium,molybdenum-nickel-palladium, etc. The active metallic components aregenerally employed in an amount of from about 0.01% to about 20.0% byweight of the total catalyst. In those instances Where the hydrocrackingcatalytic composite in the third reaction zone comprises both a groupVIII and a group VLA metallic component, these will be present in aweight ratio, of the group VIII metal to the group VIA metal, within therange of from about 0.05:1 to about 5.021. The total efiluent from thehydrocracking zone is passed into suitable separating means whereby thelight paraflinic hydrocarbons, and other various gaseous products areremoved. The resulting normally liquid hydrocarbons are subjected todistillation in a sidecut fractionator under such conditions as willyield a heart-cut having a boiling range of about 400 F. to about 650F., which heart-cut fraction is substantially free from nitrogenouscompounds, containing less than about 5.0 ppm. thereof. Thosehydrocarbons boiling below about 400 F., including butanes, are removedfrom the upper portion of the side-cut fractionator, and may betransmitted to storage pending further use either as charge to acatalytic reforming unit, or as gasoline blending components. Thecomparatively minor quantity of those unreacted hydrocarbons boilingwithin the range of from about 650 F. to about 800 F. are removed fromthe bottom portion of the side-cut fractionator, and are recycled tocombine with the normally liquid hydrocarbon effluent from the secondreaction zone, thereby forming the total liquid charge to the thirdstage of the present process. The gasoline boiling range hydrocarbons,recovered from the present process as a liquid product, are virtuallycompletely free from nitrogenous and sulfurous compounds, and,therefore, are extremely well suited for direct utilization as thecharge to a catalytic reforming unit. The middle-distillate liquidproduct, those hydrocarbons boiling within the range of about 400 F. toabout 650 F., contain less than about 5 .0 ppm. of nitrogen, and moreoften from about 1.0 to about 3.0 ppm. This middle-distillate fractionmay be subjected to further processing, for example, in still anotherhydrocracking reaction zone, and due to the physical and chemicalcharacteristics thereof, under extremely mild hydrocracking conditionswhereby there is virtually total recovery therefrom of thosehydrocarbons boiling within the gasoline boiling range. Themiddle-distillate hydrocarbon fraction is also well suited forsubsequent utilization as fuel oil. During the operation of the threestage process of the present invention, it may be found that themiddledistillate boiling range hydrocarbons are recovered containingmore than about 5.0 ppm. of nitrogen. In this event, the heavierhydrocarbons recovered from the bottom portion of the side-cutfractionator, that is, those hydrocarbons boiling within the range ofabout 650 F. to about 800 F., may be recycled to combine with the chargeto the second-stage, or clean-up reaction zone of the present process.

From the foregoing description, it is seen that the process of thepresent invention will utilize at least two catalytic composites, andthree in those instances where the first reaction zone is designed tofunction as a hydrocracking reaction zone. In those instances where theheavy hydrocarbonaceous material, to be processed within the threestages of the present invention, possesses physical and/ or chemicalcharacteristics which warrant the utilization of a severe hydrocrackingreaction zone as the first stage, any suitable acidic-type crackingcatalyst may be employed. Generally, suitable hydrocracking catalystshave been shown to consist essentially of substantially large quantitiesof chromium, tungsten, molybdenum, nickel, iron, cobalt, and mixturesthereof. For example, kieselguhr, composited with about 10% to about 50%by weight of nickel, and preferably, 30% to 50% by weight, is a suitablecatalyst for utilization under severe hydrocracking conditions. On theother hand, an acidic carrier material, comprising about by weight ofsilica and 25% by Weight of alumina, may be composited with about 25% toabout 50% by weight of chromium and/ or tungsten. In accordance with theprocess of the present invention, it is preferred that the firstreaction zone contain a hydrocracking catalyst comprising at least onemetallic component from the metals of group VIA and the iron-group ofthe periodic table, and mixtures thereof. Thus, a preferred catalyticcomposite of the present invention would comprise a carrier material ofsilica and alumina composited with about 10% to about 50% by weight ofnickel, and promoted by lesser quantities of chromium, tungsten andmolybdenum, within the range of about 2% to about 20% by weight. In anyevent, the catalytic composite, for utilization in the first reactionzone, may be manufactured by any suitable manner. A particularlyadvantageous procedure, from the standpoint of manufacturing, employsone or more impregnating techniques. Thus, where the catalyst is tocontain both nickel and tungsten, the impregnation method of preparationinvolves first preparing the suitable carrier material, for example acomposite of 75 by weight of silica and 25 by Weight of alumina, andsubsequently forming an aqueous solution of watersoluble compounds ofthe desired metals, such as nickel nitrate, nickel carbonate, tungstenchloride hydrate, etc. The alumina-silica particles, serving as theacidic carrier material, are commingled with the aforementioned aqueoussolutions, and subsequently dried at a temperature of about 200 F. Thedried composite is then subsequently oxidized in an oxidizing atmospheresuch as air, for the purpose of permanently affixing the metalliccomponents Within and throughout the carrier material. Thehightemperature oxidizing procedure is effected at an elevatedtemperature of about 1100 F. to about 1700 F., and for a period of fromabout 2 to about 8 hours or more. It is understood that the impregnatingtechnique may be elfected in any suitable, desired manner; thus, thecarrier material may be impregnated first with a nickel-containingsolution, dried and oxidized, and thereafter impregnated with atungsten-containing solution. The second impregnating step will then befollowed by subsequent drying and high-temperature oxidation procedures.On the other hand, the two aqueous solutions may be intimatelycommingled with each other, and the carrier material impregnated in asingle step. The particular means by which the catalyst, for utilizationWithin the first stage of the present process, is prepared, is notconsidered to be limiting upon the present invention. The primaryfunction, or object, of the first stage of the present process, is toelfect the substantially complete conversion of those hydrocarbonsboiling in excess of 800 E, into hydrocarbons boiling below about 800F., and this is, in part, accomplished by means of intra-stage recycleof those unreacted hydrocarbons boiling in excess of about 800 F.

As hereinbefore set forth, virtually all heavy hydrocarbonaceousmaterial boiling in excess of about 800 F. contains substantialquantities of nitrogenous and sulfurous compounds which are difiicult toremove from the higher boiling components. Therefore, as the function ofthe first stage of the present process is to convert the higher boilingcomponents into material boiling below about 800 F., the function of thesecond stage of the present process is to efiiect the substantiallycomplete destructive removal of those nitrogenous and sulfurouscompounds now boiling below about 800 F. Therefore, the second stage ofthe present process, referred to as the clean-up zone, contains anitrogen-insensitive catalyst comprising at least about 4.0% by Weightof molybdenum, calculated as the element thereof. The catalyst may befurther promoted by including therein relatively minor quantities ofiron-group metals, such as cobalt, nickel and iron. When these lattermetals are utilized in conjunction with the large quantities ofmolybdenum, they will be employed in an amount within the range of about0.2% to about 6.0% by weight thereof. In the presence of themolybdenum-containing catalyst, and under the operating conditionshereinbefore set forth, the organically-bound, nitrogen compounds areseparated at the nitrogen-hydrogen bonds to form ammonia which isreleased in a free form from the reaction media. Similarly, anysulfurous compounds, such as mercaptans, thiophenes, etc., are convertedinto hydrogen sulfide and the corresponding sulfur free hydrocarbon. Inaddition to the effective clean-up of the hydrocarbon charge stock, asignificant degree of hydrocarbon conversion occurs whereby the heaviermolecular weight hydrocarbons, boiling at a temperature within the rangeof about 650 F. to about 800 F., are converted, via highly selectivecracking reactions into hydrocarbons boiling below about 650 F. It isunderstood, however, that such selective hydrocracking reactions are notnecessarily complete in the sense that all of the hydrocarbons boilingin excess of 650 are converted to lower boiling hydrocarbon products. Inorder to maintain the high degree of selec I tive cracking, in thissecond-stage of the present process, it is preferred that the previouslymentioned catalytic components be composited with a carrier materialcomprising alumina without the addition thereto of other refractory'inorganic oxide material. The use of such material, for example,magnesia, Zirconia, thoria, boria, and especially silica, even inrelatively minor quantities, has the tendency to increase thehydrocracking activity of the catalyst, whereby the conversion reactionsresult in the unnecessary production of light, straight-chain paraffinichydrocarbons. Therefore, although the catalyst employed in the firststage of the process utilizes a composite of alumina and largequantities of silica, the catalyst within the second stage of theprocess preferably employs alumine. in a substantially pure state. Thenormally liquid hydrocarbons leaving the second-stage of the presentprocess, will generally be contaminated with less than about 10.0 ppm.of nitrogen. Through careful selection of the operating conditions andcatalyst within the second stage, the normally liquid hydrocarbons maybe produced to contain less than about 5.0 parts per million ofnitrogen. In any event, when compared to the quantity of nitrogencontained within the original heavy hydrocarbonaceous material, thecharge stock to the third-stage of the present process may be consideredsubstantially completely free from nitrogenous compounds. This is due,at least inpart, to the method of concentrating such nitrogenouscompounds Within a hydrocarbon fraction boiling below about 800 F., andprocessing such fraction within the second stage of the present process.

The third stage of the present process is designed to convert the nowsubstantially nitrogen-free hydrocarbon fraction boiling in excess ofthe middle-distillate boiling range, into hydrocarbons boiling withinboth the middledistillate and gasoline boiling ranges; in addition, theutilization of a selective catalyst within the third stage of thepresent process will effect substantial conversion of themiddle-distillate boiling range hydrocarbons into gasoline boiling rangehydrocarbons without the usual attendant conversion to light parafiinichydrocarbons such as methane, ethane and propane. In view of the factthat the total hydrocarbon charge to this third reaction zone maycontain from about 3.0 to about 5 .0 ppm. of nitrogen, it is to greatadvantage to utilize certain catalytic composites therein, and whichcomposites are most effective for the mild hydrocracking of hydrocarbonsboiling within the range of 650 to about 800 F., although containingthese residual nitrogenous compounds. By the same token, as hereinabovedescribed, the catalyst is selected to effect substantial conversion ofmiddle-distillate hydrocarbons into gasoline boiling range hydrocarbons.To illustrate, alumina, containing relatively minor quantities of silica(approximately 12% by weight) possesses a high degree of activity inregard to the destructive removal of nitrogenous compounds. Likewise,silica is a good hydrocracking catalyst when containing a relativelyminor quantity of alumina, while on the other hand, is not a goodnitrogen remover. Similarly, the metallic components of the catalystdisposed within the third stage, or hydrocracking reaction zone, Willexhibit similar propensities. For example, as indicated in regard to thefirst reaction zone, when the latter contains a suitable hydrocrackingcatalyst, large quantities of nickel exhibit high activity in regard tohydrocracking, but do not possess a relatively high degree of activityin regard to the removal of nitrogenous compounds. On the other hand,molybdenum may be considered a good nitrogen remover, but is notrelatively active as either a hydrocracking or hydrogenation catalyst.Similarly, metals selected from the platinum-group of the periodic tableare considered excellent hydrogenation catalysts, and, althougheffecting hydrocracking to a certain degree, are not normally consideredin the classification of hydrocracking catalysts. I have found thatcatalytic composites which comprise at least one metallic componentselected from groups VIA and VIII of the periodic table, and mixturesthereof, including platinum, palladium, nickel and/or molybdenum, etc.,and composited with silica and from about to about 90% by weight ofalumina, constitute preferred hydrocracking catalysts for utilizationwithin the third stage of the process of the present invention. Suchcatalysts have a relatively high degree of activity in regard to theconversion of hydrocarbons boiling Within the middle-distillate boilingrange, and, more importantly, effect the substantially completeconversion of those hydrocarbons boiling Within the range of 650 F. toabout 800 F. It is significant that such activity is substantiallyunaffected even by the relatively minor quantities of nitrogen, lessthan about 5.0 ppm. contained within the charge to the third-stagereaction zone.

The carrier material, for utilization within the catalyst employed inthe first stage of the present process, unless of course such stagecomprises a thermal cracking unit of the single-coil or double-coiltype, may be alumina, magnesia, fullers earth, montmorillonite, silica,kieselguhr, etc. A suitable carrier material may consist, for example,of a major proportion of precipitated silica composited with one or morehydrated oxides such as hydrated alumina, hydrated zirconia, andhydrated thoria. When synthetically-produced, the solid carrier materialmay be made in any suitable manner including separate, successive orcoprecipitation methods. For example, silica may be prepared bycommingling Water glass and a mineral acid under such conditions as willprecipitate a silica hydrogel. The silica hydrogel is subsequentlywashed with Water containing a small amount of a suitable electrolytefor the purpose of removing sodium ions. The oxides of other compounds,when desired, may be prepared by reacting a basic reagent such asammonium hydroxide, ammonium carbonate, etc., with an acid salt solutionof the metal, as for example, the chloride, sulfate, nitrate, etc., orby adding an acid to an alkaline salt of the metal such as, for example,commingling sulfuric acid with sodium aluminate, etc. When it isadvantageous to prepare the carrier material in the form of particles ofuniform size and shape, this may be readily accomplished by grinding thepartially dried oxide cake, with a suitable lubricant such as stearicacid, resin, graphite, etc., subsequently forming the particles in anysuitable pelleting or extrusion apparatus. The preferred carriermaterial, for utilization in the first stage of the present invention,comprises at least two refractory inorganic oxides, and such a compositemay be prepared by the separate precipitation method, in which theoxides are precipitated separately, and then mixed, preferably in thewet state; when successive precipitation methods are employed, the firstoxide is precipitated as previously set forth, and the wet slurry,either with or without prior washing, is composited with a salt of theother component. Thus, a precipitated, hydrated silica, substantiallyalkaline free, is suspended in an aqueous solution of aluminum chlorideand zirconium chloride following which precipitated hydrated alumina andprecipitated hydrated zirconia are deposited upon the silica gel by theaddition of an alkaline precipitant, such as ammonium hydroxide. Theresulting mass of hydrated oxide is water washed, dried and calcined atabout 1400 F. Another possible method of manufacture consists ofcommingling an acid such as hydrochloric acid, sulfuric acid, etc., withcommercial water glass under conditions to precipitate silica, washingthe precipitate with acidulated water or other means to remove sodiumions, commingling with an aluminum salt such as aluminum chloride,and/or some suitable zirconium salt, etc., and either adding a basicprecipitant such as ammonium hydroxide to precipitate alumina and/orzirconia, or forming the desired oxide or oxides through the thermaldecomposition of the salt as the case may permit. Thesilica-alumina-zirconia cracking component may be formed by adding thealuminum and/or zirconium salts together or separately. It is understoodthat the particular means employed for the manufacture of thehydrocracking catalyst, utilized in the first reaction 18 zone, is notconsidered to be a limiting feature of the process of the presentinvention.

As hereinbefore set forth, the carrier material utilized within thesecond stage is preferred to be alumina. Since the primary function ofthis second stage is the destructive removal of nitrogenous andsulfurous compounds, it is considered advantageous to limit theconversion reactions in a manner such that little or no light parafiinichydrocarbons are produced. The alumina may be prepared by adding areagent such as ammonium hydroxide, ammonium carbonate, etc., to a saltof aluminum such as aluminum chloride, aluminum nitrate, aluminumacetate, etc., in an amount to form aluminum hydroxide. Aluminumchloride is generally preferred as the aluminum salt to be employed, notonly for convenience in subsequent washing and filtering procedures, butalso it appears to give the best results. The resulting precipitate is,upon drying, converted to alumina. The alumina particles may take theform of any desired shape such as spheres, pills, pellets, cakes,extrudates, powder, granules, etc. A particularly preferred form ofalumina is the sphere, and these spheres may be continuouslymanufactured by passing droplets of an alumina hydrosol into an oil bathwhich is maintained at an elevated temperature, and retaining thedroplets in said oil bath until the same set into firm hydrogelspheroids. This particular method, commonly referred to as the oil-dropmethod, is described in detail in U.S. Patent No. 2,620,314, issued toJames Hoekstra.

With respect to the carrier material employed as a part of the catalystdisposed Within the [third reaction zone, it is preferred to utilize atleast tWo refractory inorganic oxides, and preferably alumina andsilica. When silica and alumina are employed in combination, the latterwill be present within an amount of from about 10% to about by Weight.Thus, the carrier material within the third-stage of the present processmay comprise the following: 88% by weight of silica and 12% by Weight ofalumina, 75% by weight of silica and 25% by weight of alumina, 88% byweight of alumina and 12% by weight of silica. Following the formationof the carrier material, the catalytically active metallic componentsare composited therewith. The catalyst comprise at least one metalliccomponent selected from the metals of groups VIA and VIII of theperiodic table, and includes the platinum-group metals, the iron-groupmetals, molybdenum, tungsten, and chromium. These metallic componentsmay be incorporated within the alumina-silica carrier material in anysuitable manner. impregnating techniques may be advantageously employedby first forming an aqueous solution of a watersoluble compound of thedesired metal such as platinum chloride, palladium chloride,chloroplatinic acid, chloropalladic acid, ammonia molybdate, nickelnitrate hexahydrate, tungsten chloride, dinitrito-diamino platinum,etc., and commingling the resulting solution with the alumina-silica ina steam drier. Other suitable metalcontaining solutions which may beemployed are colloidal solutions or suspensions including the desiredmetal cyanides, metal hydrom'des, metal oxides, metal sulfides, etc.Where these solutions are not water-soluble at the temperature employed,other suitable solvents such as alcohols, ethers, etc., may be utilized.The final catalytic composite, after all of the catalytic components arepresent therein, is dried for a period of from about 2 to about 8 houror more, and subsequently oxidized in an oxidizing atmosphere such asair, at an elevated temperature of about 1100 F. to about 1700 F., andfor a period of from about one to about eight hours or more. Followingthe high-temperature oxidation procedure, the catalyst may be reducedfor a period ranging from about /2 hour to about 1 hour in the presenceof hydrogen, at a temperature within the range of about 700 F. to about1000 F. Where convenient, the catalyst may be reduced in situ, that is,by placing the catalyst within the third reaction zone, subjecting thesame to an imposed hydrogen purge of the system at a temperature ofabout 700 F.

The total quantity of metallic components of the catalyst disposedwithin the third reaction zone, is within the range of from about 0.01%to about 20.0% by weight of the total catalyst. The group VIA metal,such as chromium, molybdenum, or tungsten, is usually present within therange of from about 0.5% to about 10.0% by weight of the catalyst. Thegroup VIII metals, which may be divided into two sub-groups, are presentin an amount of from about 0.01% to about 10.0% by weight of the totalcatalyst. When an iron sub-group metal, such as iron, cobalt, or nickel,is employed, it is present in an amount of from about 0.2% to about10.0% by weight, while, if a platinum-group metal such as platinum,palladium, iridium, etc., is employed, it is present in an amount withinthe range of from about 0.01% to about 5.0% by weight of the totalcatalyst. When the metallic component of the hydrocracking catalystconsists of both a group VIA metal and a group VIII metal, it willcontain metals of the above groups in a ratio of from about 0.05:1 toabout 5.0:1 of the group VIH metal component to the group VIA metalliccomponent. Therefore suitable catalysts for utilization within the thirdreaction zone, include, but are not considered to be limited to, thefollowing: 6.0% by weight of nickel and 0.2% by weight of molybdenum;6.0% by weight of nickel and 0.2% by weight of platinum; 0.4% by weightof platinum; 6.0% by weight of nickel and 0.2% by weight of palladium;0.4% by weight of palladium, etc.

The catalyst employed within the third stage of the process of thepresent invention is preferably disposed within the reaction zone as afixed bed. As a result of the physical and chemical characteristics ofthe charge stock to the third stage, the operating conditions thereinare relatively mild. For example, the operating temperature at which thecatalyst is maintained may be at least about 50 F. less than thetemperature employed within the second reaction zone. It is not unusual,in the process of the present invention, to operate the third reactionzone at a temperature which is as much as 150 F. lower than thetemperature within the second reaction zone. Furthermore, there existsthe requirement for a lesser quantity of hydrogen within the thirdstage, and the rate of liquid charge thereto may be substantiallyincreased. The total efltluent from the hydrocracking reaction zone maybe passed to a suitable high-pressure, low-temperature separation zone,from which a hydrogenrich gas stream is withdrawn and recycled to supplyat least a portion of the hydrogen which is admixed with the liquidhydrocarbon charge stock. It is understood that the broad scope of thepresent invention is not to be unduly limited to a particular catalyst,or to a particular method of manufacturing the same. The utilization ofany of the previously mentioned catalytic composites, whether in thefirst, second or third reaction zones, at operating conditions whichvary within the limits hereinbefore set forth, do not necessarily yieldresults which are equivalent to those obtained through the utilizationof other catalytic composites or other operating conditions. Anessential feature of the present invention is the separate, distinctlyintegrated three stages within which the overall process is effected.Through the utilization of the process of the present invention, greaterconcentrations of hydrocarbons boiling within the gasoline andmiddle-distillate boiling ranges are produced from those hydrocarbonswhich boil in excess of the middle-distillate boiling range.Furthermore, greater concentrations of gasoline boiling rangehydrocarbons may be produced from those middle-distillate boiling rangehydrocarbons withdrawn as a product from the third stage pf the process.The overall picture results in a. substantial reduction in the quantityof light paraffinic hydrocarbons otherwise resulting from thenon-selective singlestage hydrocracking of similar heavyhydro'carbonaceous material. Furthermore, the process of the presentinvention results in a gasoline boiling range hydrocarbon productsubstantially free from unsaturated paraffinic hydrocarbons; thegasoline boiling range product is, therefore, extremely well suited ascharge stock to a catalytic reforming unit for the purpose of furtherincreasing the octane rating thereof. Thus, through the utilization ofthe process of the present invention, a hydrocarbon charge stock, havinga boiling range of from about 700 F. to about 1000 F. or higher, may besubstantially completely converted into hydrocarbons boiling within thegasoline boiling range, notwithstanding the presence of exceedinglyexcessive quantities of nitrogenous and sulfurous compounds.Furthermore, these high volumetric yields are obtained Without the usualexceedingly high yield loss due to the formation of an excessivequantity of light paraffinic hydrocarbons, and without experiencing therapid deactivation of the catalytic composite employed.

The process of the present invention may comprise either a batch or acontinuous-type operation. When utilizing the continuous-type operation,which is the particularly preferred manner of efiecting the present invention, the various catalytic composites may be disposed, in theirrespective reaction zones, as fixed beds, as illustrated in theaccompanying drawing, and maintained under the desired operatingconditions. The hydrocarbons, and hydrogen, are continuously charged tothe re action zone, passing in downward flow through the catalyst, or,Where desired, either in upward flow or radialflow. The operation may beeifected as a moving-bed type, or a suspensoid-type of operation, inwhich the catalyst and hydrocarbons are passed as a slurry through thereaction zone.

The following examples are given to further illustrate the process ofthe present invention, and to indicate the benefits to be affordedthrough the utilization thereof. It is understood that the examples aregiven for the sole purpose of illustration, and are not intended tolimit the generally broad scope and spirit of the appended claims.

EXAMPLE I A Mid-Continent vacuum gas oil, having a boiling rangeindicating an initial boiling point of about 600 F. and a distillationpoint (ASTM Method D-86) of 950 F., the latter indicating an end pointof about 1000 F., was subjected to processing in accordance with thedescription of the second-stage of the present process. The gas oil wascontaminated by 252 ppm. of nitrogen, and contained 0.35% by weight ofsulfur. The catalyst employed consisted of an alumina-silica carriermaterial, comprising 88% by weight of alumina, impregnated with a singleimpregnating solution containing molybdic acid and nickel nitratehexahydrate in amounts to yield a final catalyst containing 6.4% byweight of molybdenum and 2.4% by Weight of nickel. The catalyst wasmaintained at a temperature of 750 F., a pressure of 1500 pounds persquare inch, and the liquid charge rate was equivalent to 0.3 liquidhourly space velocity, in the presence of 4500 standard cubic feet perbarrel of hydrogen. Under these conditions, the normally liquidhydrocarbon product contained nitrogen in an amount of 21 ppm.

To illustrate the function of the first stage of the present process,whether utilizing a severe hydrocracking reaction zone, or a thermalcracking reaction zone, a Mid- Continent gas oil, containing nohydrocarbons boiling in excess of 800 F., was processed in a likemanner, again simulating the second-stage of the present process. Thegas oil was contaminated with total nitrogen in an amount of 252 ppm.and total sulfur in an amount of 0.35% by weight. These and other chargestock inspections are given in the following Table I.

Percent 650 F Total Nitrogen, wt. ppm 0.99 Total Sulfur, Wt. PercentProduct Distribution:

Butanes- 180 R, ER, vol. percent 180 F.-400 F., E.P., vol. percent 400F.650 F., E.P., vol. per

650 F. and Heavier, vol. percent Total Volumetric Yield 1 -0; LightParafiinic Hydrocarbons=L80 wt. percent.

The total liquid product effluent, including butanes, had a nitrogencontent of slightly less than 1.0 ppm. and a total sulfur content of0.022 Wt. percent. These data indicate that the nitrogenous andsulfurous compounds may be effectively completely removed from thosehydrocarbons boiling at a temperature less than about 800 F., whereas,these compounds, particularly the nitrogenous compounds, are difiicultto remove from those hydrocarbon fractions boiling in excess of 800 F.In addition to the rather effective clean-up of the charge to the secondreaction zone, there is evidence of a considerable amount of selectivehydrocracking taking place as shown by the shift in boiling range. Theproduct distribution, as indicated in Table I, was obtained by preciselaboratory fractionation in a 30-plate distillation column, and includesthe butanes removed along with the light parafiinic hydrocarbons priorto the laboratory distillation. It is significant that the lightparafiinic hydrocarbon yield was less than 2.0% by weight of the totalcharge, and that the total volumetric yield was in excess of 100%.

EXAMPLE H The charge stock employed in this example (illustrating thethird stage), was the liquid hydrocarbon product resulting from theMid-Continent gas oil utilized in Example I (illustrating the operationof the second-stage of the process). The catalyst employed in thisexample consisted of a carrier material of 88% by weight of silica and12% by weight of alumina, impregnated with sutficient palladium chlorideto result in a final composite containing 0.4% by weight of palladium.The operating conditions were, a pressure of 1500 pounds per squareinch, a temperature of 575 F., a liquid hourly space velocity of 1.0 anda hydrogen rate of 3000 standard cubic feet per barrel of liquid charge.It should be noted Table II MILD HYDROCRACKING, MID-CONTINENT GAS OILPRODUCT PROPERTIES Gravity, API 60 F. 49.1 ASTM, D-86 distillation, F.:

IBP 156 220 30% 305 50% 445 70% 560 22 650 End point 688 Percent 400 F45.0 Percent 650 F. 90.0

Product distribution:

Butanes 180 F., E.P 11.8 180 F.-400 F., E.P. 46.1 400 F.-650 F., E.P.40.3 650 F. and heavier 8.9

Total volumetric yield 107.1

1 C1-C3 light parafl'inic hydrocarbons:1.64 wt. percent.

As previously stated in regard to Example I, the indicated productdistribution accounts for those butanes inadvertently removed from thetotal reaction zone efiluent while separating the light paraiiinichydrocarbons therefrom. The product distribution is, however, based uponan overall material balance of 99.9%. It is again significant that thetotal light paraifinic hydrocarbon yield was less than about 2.0% byweight of the total liquid charge. In addition, the total volumetricyield was significantly in excess of Of greater significance, is thefact that only 8.9 volume percent of the total liquid charge to thethird stage of the present process was unreacted. As indicated in theproduct distribution, there resulted 57.9% by weight of gasoline boilingrange hydrocarbons and 40.3% by volume of middle-distillate boilingrange hydrocarbons.

The foregoing examples clearly indicate the method of the presentinvention and the various benefits to be afforded through theutilization thereof. The three-stage process of the present inventionhas been shown to result in exceedingly large volumetric yields ofgasoline boiling range hydrocarbons and middle-distillate hydrocarbonswhile processing heavy hydrocarbonaceous material sevcrly contaminatedby excessive quantities of both nitrogenous and sulfurous compounds.

I claim as my invention:

1. A process for the conversion of hydrocarbon oil containingnitrogenous compounds and hydrocarbons boiling above about 800 R, whichcomprises cracking said oil to form hydrocarbons heavier than gasolineand boiling below about 800 F., reacting the last-named hydrocarbonswith hydrogen to convert nitrogenous compounds therein to ammonia,separating the ammonia from normally liquid hydrocarbons, andhydrocracking at least a portion of the latter in the presence ofhydrogen and a hydrocracking catalyst.

2. A process for converting hydrocarbonaceous material containingnitrogenous compounds and hydrocarbons boiling in the range of fromabout 700 F. to about 1000 E, into lower boiling hydrocarbon products,which comprises cracking said hydrocarbonaceous material in a firstreaction zone, removing light paraffinic hydrocarbons from the resultantefiluent, and thereafter separating the remaining normally liquidhydrocarbons into a heavy fraction having an initial boiling point inexcess of a temperature of about 800 F. and a light fraction heavierthan gasoline and boiling below about 800 F., recycling said heavyfraction to combine with said hydrocarbonaceous material; reacting saidlight fraction with hydrogen in a second reaction zone to convertnitrogenous compounds therein to ammonia, removing ammonia and normallygaseous hydrocarbons from the resultant second zone efiiuent, andpassing the normally liquid hydrocarbons, along with additionalhydrogen, into a third reaction zone maintained at hydrocrackingconditions; removing normally gaseous hydrocarbons from the resultantthird zone efiluent and separating the normally liquid hydrocarbons intoa first fraction having an end boiling point of about 400 F. to about450 F., a second traction having an initial boiling point of about 400F. to about 450 F. and an end boiling point of about 650 F. to about 700F., and a third fraction boiling at a temperature in excess of about 650F. to about 700 F., and recycling at least a portion of said thirdfraction to combine with said hydrogen and the normally liquidhydrocarbons from said second reaction zone, prior to conversion thereofin said third reaction zone.

3. The process of claim 2 further characterized in that saidhydrocarbonaceous material is initially stabilized to produce a lightfraction having an end boiling point below about 800 F., and a heavierfraction having an initial boiling point of about 800 F., said heavierfraction passing into said first reaction zone.

4. The process of claim 2 further characterized in that said firstreaction zone is maintained at thermal cracking conditions.

5. The process of claim 2 further characterized in that said firstreaction zone contains a hydrocracking catalyst comprising at least onemetallic component from the metals of groups VIA and the iron-group ofthe periodic table, and mixtures thereof.

6. A process for converting hydrocarbonaceous mate rial having a boilingrange of from about 700 F. to about 1000 F., and containing nitrogenouscompounds, into lower boiling hydrocarbon products which comprisesinitially fractionating said hydrocarbonaceous material to produce afirst light fraction containing those hydrocarbons boiling below about800 F., and a first heavy fraction having an initial boiling point ofabout 800 F., cracking said first heavy fraction in a first reactionzone, separating the resultant efiluent into a second light fraction anda second heavy fraction, the former comprising hydrocarbons heavier thangasoline and boiling below about 800 F. and the latter having an initialboiling point of about 800 F., recycling said second heavy fraction tocombine with said first heavy fraction prior to conversion in said firstreaction zone, and combining said second light fraction with said firstlight fraction; reacting the resultant light fraction mixture withhydrogen in a second reaction zone to convert nitrogenous compoundstherein to ammonia, removing ammonia and normally gaseous hydrocarbonsfrom the resultant second zone efliuent, and passing the normally liquidhydrocarbons, along with additional hydrogen, into a third reaction zonemaintained at hydrocracking conditions; removing normally gaseoushydrocarbons from the third reaction zone efiluent and separating thenormally liquid hydrocarbons into a first fraction having an end boilingpoint of about 400 F. to about 450 F., a second fraction having aninitial boiling point of about 400 F. to about 450 F. and an end boilingpoint of about 650 F. to about 700 F., and a third fraction boiling at atemperature in excess of about 650 F. to about 700 F., recycling atleast a portion of said third fraction to combine with the normallyliquid hydrocarbons from said second reaction zone and hydrogen, priorto conversion thereof in said third reaction zone.

7. The process of claim 6 further characterized in that said thirdreaction zone contains a catalyst comprising at least one metalliccomponent selected from the metals of groups VIA and VIII of theperiodic table, and mixtures thereof.

8. The process of claim 6 further characterized in that said thirdreaction zone contains a catalyst comprising a group VIA and a groupVIII metallic component, the ratio of said group VIII metallic componentto said group VIA metallic component being within the range of about0.05:1 to about .021.

9. The process of claim 6 further characterized in that said thirdreaction zone contains a catalyst comprising at least one platinum-groupmetallic component composited with silica and from about to about 90% byweight of alumina.

10. The catalyst of claim 9 further characterized in '24 that saidplatinum-group metallic component is palladium.

11. The catalyst of claim 9 further characterized in that saidplatinum-group metallic component is platinum.

12. A process for converting nitrogen-contaminated hydrocarbonaceousmaterial, having a boiling range of from about 700 F. to about 1000 F.,into lower boiling hyrocarbon products substantially free fromnitrogenous compounds, which comprises initially stabilizing saidhydrocarbonaceous material to produce a first light fraction containingthose hydrocarbons boiling below about 800 F., and a first heavyfraction having an initial boiling point of about 800 F; cracking saidfirst heavy fraction in a first reaction zone containing a crackingcatalyst comprising at least one metallic component from the metals ofgroups VIA and the iron-group of the periodic table, and mixturesthereof, separating the resultant etfiuent into a second light fractioncomprising hydrocarbons heavier than gasoline and boiling below about800 F. and a second heavy fraction containing hydrocarbons boiling inexcess of a temperature of about 800 F., recycling the second heavyfraction to combine with said first heavy fraction prior to theconversion thereof in said first reaction zone, and combining saidsecond light fraction with said first light fraction; reacting theresulting light fraction mixture with hydrogen in a second reaction zonecontaining a catalyst comprising from about 4% to about 45% by weight ofmolybdenum to convert nitrogenous compounds therein to ammonia, removingammonia and normally gaseous hydrocarbons from the resultant second zoneeflluent, and passing the normally liquid hydrocarbons, along withadditional hydrogen, into a third reaction zone maintained athydrocracking conditions and containing a catalyst comprising from about0.01% to about 5.0% by weight of platinum composited with silica andfrom about 10% to about by weight of alumina; removing normally gaseoushydrocarbons from the resultant third zone efiluent and separating thenormally liquid hydrocarbons into a first fraction having an end boilingpoint of about 400 F. to about 450 F., a second fraction having aninitial boiling point of about 400 F. to about 450 F. and an end boilingpoint of about 650 F. to about 700 F., and a third fraction boiling at atemperature in excess of about 650 F. to about 700 F., recycling atleast a portion of said third fraction to combine with the normallyliquid hydrocarbons from said second reaction zone and hydrogen, priorto conversion thereof in said third reaction zone.

13. The process of claim 12 further characterized in that said secondreaction zone is maintained at a temperature within the range of fromabout 500 F. to about 1000 F. and said third reaction zone is maintainedat a temperature at least about 50 F. lower than the temperature in saidsecond reaction zone.

14. A process for converting nitrogen-contaminated hydrocarbonaceousmaterial, having a boiling range of from about 700 F. to about 1000 F.,into lower boiling hydrocarbon products, substantially free fromnitrogenous compounds, which comprises initially stabilizing saidhydrocarbonaceous material to produce a first light fraction containingthose hydrocarbons boiling below about 800 F., and a first heavyfraction having an initial boiling point of about 800 F.; cracking saidfirst heavy fraction in a first reaction zone, separating the resultanteffluent into a second light fraction comprising hydrocarbons heavierthan gasoline and boiling below about 800 F. and a second heavy fractioncontaining hydrocarbons boiling in excess of a temperature of about 800F., recycling the second heavy fraction to combine with said first heavyfraction prior to the cracking thereof in said first reaction zone, andcombining said second light fraction with said first light fraction;reacting the resulting light fraction'mixture with hydro- 25 gen in asecond reaction zone containing a catalyst comprising alumina, fromabout 4% to about 45% by weight of molybdenum to convert nitrogenouscompounds therein to ammonia, and from about 0.2% to about 6% by weightof nickel; removing ammonia and normally gaseous hydrocarbons from theresultant second zone efliuent, and passing the normally liquidhydrocarbons, along with additional hydrogen, into a third reaction zonemaintained at hydrocracking conditions and containing a catalystcomprising from about 0.01% to about 5.0% by weight of palladiumcomposited with silica and from about 10% to about 90% by weight ofalumina; removing normally gaseous hydrocarbons from the resultant thirdzone efiiuent and separating the normally liquid hydrocarbons into afirst fraction having an end boiling point of about 400 F. to about 450F., a second fraction having an initial boiling point of about 400 F. toabout 450 F. and an end boiling point of about 650 F. to about 700 F.,and a third fraction having an initial boiling point in excess of atemperature of about 650 F. to about 700 F., recycling at least aportion of said third fraction to combine with the normally liquidhydrocarbons from said second reaction zone and hydrogen, prior toconversion thereof in said third reaction zone; the process furthercharacterized in that said second reaction zone is maintained at atemperature within the range of from about 500 F. to about 1000 F. andsaid third reaction zone is maintained at a temperature at least about50 F. lower than the temperature in said second reaction zone.

15. The process of claim 1 further characterized in that saidhydrocarbon oil has a boiling range of from about 700 F. to about 1000F.

16. The process of claim 1 further characterized in that said oil isthermally cracked.

17. A process for the conversion of hydrocarbon oil containingnitrogenous compounds and hydrocarbons boiling above and below about 800R, which comprises separating said oil into a light fraction boilingbelow about 800 F. and a heavy fraction boiling above about 800 F.,cracking said heavy fraction to form additional hydrocarbons heavierthan gasoline and boiling below about 800 R, combining the last-namedhydrocarbons with said light fraction, reacting the resultant mixturewith hydrogen to convert nitrogenous compounds therein to ammonia,separating the ammonia from normally liquid hydrocarbons, andhydrocracking at least a portion of the latter in the presence ofhydrogen and a hydrocracking catalyst.

References Cited in the file of this patent UNITED STATES PATENTS2,885,346 Kearby et a1. May 5, 1959

1. A PROCESS FOR THE CONVERSION OF HYDROCARBON OIL CONTAININGNITROGENOUS COMPOUNDS AND HYDROCARBONS BOILING ABOVE ABOUT 800*F., WHICHCOMPRISES CRACKING SAID OIL TO FORM HYDROCARBONS HEAVIER THAN GASOLINEAND BOILING BELOW ABOUT 800*F., REACTING THE LAST-NAMED HYDROCARBONSWITH HYDROGEN TO CONVERT NITROGENOUS COMPOUNDS THEREIN TO AMMONIA,SEPARATING THE AMMONIA FROM NORMALLY LIQUID HYDROCARBONS, ANDHYDROCRACKING AT LEAST A PORTION OF THE LATTER IN THE PRESENCE OFHYDROGEN AND A HYDROCRACKING CATALYST.